U.S. patent application number 10/666018 was filed with the patent office on 2004-07-22 for vascular pressure differential device and method of use.
Invention is credited to Schwartz, Robert S., Stassen, David William, Van Tassel, Robert A..
Application Number | 20040143319 10/666018 |
Document ID | / |
Family ID | 32033583 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040143319 |
Kind Code |
A1 |
Schwartz, Robert S. ; et
al. |
July 22, 2004 |
Vascular pressure differential device and method of use
Abstract
The present invention modifies the compliance of a vascular
system by providing an elastic member, capable of reducing peak
pressure and blood flow from the heart. These embodiments further
allow for reduction of peak systolic pressure while increasing
diastolic pressure and flow. In one embodiment, the device consists
of an anchoring stent, having an elastic member with a passage for
blood flow. This device is implanted percutaneously into a desired
vessel location. The elastic member begins to "give" when blood
pressure reaches a desired level. Additionally, the spring constant
of the elastic member may be externally modified to change the
compliancy. By precisely modifying the properties of the elastic
member, normal arterial compliancy may be restored.
Inventors: |
Schwartz, Robert S.;
(Rochester, MN) ; Van Tassel, Robert A.;
(Excelsior, MN) ; Stassen, David William; (Edina,
MN) |
Correspondence
Address: |
INSKEEP INTELLECTUAL PROPERTY GROUP, INC
1225 W. 190TH STREET
SUITE 205
GARDENA
CA
90248
US
|
Family ID: |
32033583 |
Appl. No.: |
10/666018 |
Filed: |
September 17, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60412122 |
Sep 17, 2002 |
|
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60473988 |
May 28, 2003 |
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Current U.S.
Class: |
623/1.24 ; 604/9;
623/1.3 |
Current CPC
Class: |
A61B 17/0057 20130101;
A61F 2250/0002 20130101; A61F 2002/30074 20130101; A61F 2/2475
20130101; A61F 2002/3067 20130101; A61F 2/06 20130101; A61F
2230/0078 20130101; A61F 2002/30548 20130101; A61F 2/2424 20130101;
A61F 2/07 20130101; A61F 2002/068 20130101; A61F 2/89 20130101;
A61F 2250/0013 20130101; A61F 2210/0057 20130101 |
Class at
Publication: |
623/001.24 ;
623/001.3; 604/009 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. A device for responding to an elevated pressure condition in a
patient comprising: an implant; a pressure differential member
disposed within said implant; said implant sized and shaped so as
to place said pressure differential member in communication with
both an arterial side and a venous side of a vascular system; and
said pressure differential member configured for directing pressure
increases in said arterial side to said venous side of said
vascular system.
2. A device according to claim 1, wherein said pressure
differential member is a valve.
3. A device according to claim 2, wherein said valve includes a
pressure threshold actuation mechanism so as to cause opening of
said valve at a predetermined pressure.
4. A device according to claim 3, wherein said valve is sized and
shaped for placement in a heart wall separating said venous side
from said arterial side of said vascular system.
5. A device according to claim 2, wherein said valve is sized and
shaped for placement between a descending aorta and a inferior vena
cava of a patient.
6. A device according to claim 1, wherein said pressure
differential member is a membrane.
7. A device according to claim 6, wherein said membrane is sized
and shaped for placement in an atrial wall separating a left
ventricle of said arterial side and a right ventricle of said
venous side.
8. A device according to claim 1, wherein said implant is a valve
holder and said pressure differential is a valve.
9. A device according to claim 1, wherein said implant is a lumen
and said pressure differential is a valve.
10. A method of controlling body lumen pressure fluctuations in a
vascular system of a patient comprising: diagnosing a patient
having an elevated pressure condition in a body lumen; placing a
pressure differential device between an arterial side of said
vascular system and a venous side of said vascular system;
diverting undesirable pressure increases in said arterial side of
said vascular system through said pressure differential device into
said venous side of said vascular system.
11. A method according to claim 10, wherein said diverting includes
diverting said pressure increases through a wall of the heart.
12. A method according to claim 10, wherein said diverting includes
diverting said pressure increases through a lumen of said pressure
differential device from a descending aorta to an inferior vena
cava.
13. A method according to claim 10, wherein said pressure
differential device includes a valve and diverting includes
diverting fluid through said valve.
14. A method according to claim 10, wherein said pressure
differential device includes a distensible membrane and diverting
includes diverting pressure against said distensible membrane.
15. A method according to claim 10, further including absorbing
said undesirable pressure increases using a compliance device
located in an aorta of said vascular system.
Description
[0001] This application claims priority to provisional application
No. 60/412,122 filed on Sep. 17, 2002 entitled "Aortic Shock
Absorber" and to provisional application No. 60/473,988 filed May
28, 2003 entitled "Aortic Shock Absorber, V.2", both of which are
incorporated herein by reference. This application also
incorporates by reference co-pending U.S. application Ser. No.
10/192,402 filed Jul. 8, 2002 entitled "Anti-Arrhythmia Devices And
Methods Of Use."
FIELD OF INVENTION
[0002] The present invention relates to medical devices. More
particularly, this invention relates to passive devices that absorb
aortic blood pressure shock, restoring elasticity to cardiovascular
systems.
BACKGROUND OF THE INVENTION
[0003] Hypertension, also known as high blood pressure, can cause
heart, kidney, brain and arterial damage, leading to
atherosclerosis, stroke, heart attack, heart failure, and other
vascular related diseases. The exact cause of hypertension is often
difficult to determine, but several factors are thought to
contribute to the condition, including obesity, heavy alcohol use,
family history, high salt intake, diabetes, stiffening of the
vascular system, and aging. Stress, low calcium intake, and
resistance to insulin may also be contributing factors.
Additionally, secondary forms of hypertension can occur due to
certain medications, narrowing of the kidney arteries, or
pregnancy.
[0004] Almost one-third of every American adult has high blood
pressure, an estimated 58 million people. Of the 58 million with
high blood pressure, nearly one-third are unaware of it, and almost
two-thirds are unable to control it.
[0005] Hypertension has an important and common link with
congestive heart failure due to both afterload increases and
deleterious changes in pressure-flow relationships of the left
ventricle and aorta, the loading conditions of the left
ventricle.
[0006] As the aorta ages, it loses compliance, or elasticity,
through wall thickening, fibrous scar formation, cellular
degeneration, expansion, and elastin degradation. The aortic wall
and smaller vessels undergo hypertrophy, or fibrous thickening, in
response to chronically elevated blood pressures. This hypertrophy
causes increased pressure rises with accelerating rates of change,
creating a positive feedback process as further described below.
Such effects are thought to cause damage to the arterial wall
tissue, resulting in further decreased compliance. Decreased
compliance causes increased systolic pressure, which in turn causes
more rapid and severe vascular wall degeneration. This sequence
becomes a vicious circle of feedback events that progressively
deteriorate normal aortic compliance functions, increase blood
pressure, and eventually degrade left ventricular systolic and
diastolic function, leading to heart failure syndromes.
[0007] The normal human aorta and large capacitance vessels are
only partially resistive. The pressure-flow relationship is also
partially capacitive, whereby the blood flow leads pressure for
pulsatile waveforms as induced by the bolus of blood injected by
the heart with each cardiac cycle. As the human vessel ages, it
becomes significantly stiffer with the result being a more purely
resistive structure. This means that the blood pressure rises
simply because of the arterial stiffness, resulting in more work
per heartbeat that the heart must expend.
[0008] Peak pressure increases in non-compliant vascular systems
are believed to induce stress. The amount of stress is related to
several factors, including blood pressure, blood viscosity, and
velocity of the blood. This stress triggers the body's injury
response mechanism which subsequently interferes with the
functionality of the artery.
[0009] Several studies have examined the proximal and distal
thoracic aortic area and distensibility through the cardiac cycle,
and found a direct relationship with exercise intolerance in
elderly patients. Patients with diastolic dysfunction have higher
resting heart rates and systolic blood pressure, greater left
ventricular mass, aortic wall thickness and mean aortic flow
velocity. Thus, poor exercise tolerance strongly correlates with
reduced aortic compliance and pressure-distensibility.
[0010] Lifestyle changes such as exercise and weight loss may help
reduce hypertension. In addition, medications remain a common
treatment prescribed by doctors, and may include diuretics,
beta-blockers, calcium channel blockers, angiotensin-converting
enzyme (ACE) inhibitors, angiotensin receptor blockers, or alpha
blockers. Additionally, severe hypertension is treated with potent
vasodilators such as hydralazine, minoxidil, diazoxide,
nitroprusside, or similar drugs.
[0011] In this regard, the following chart illustrates the results
of typical ACE inhibitor therapy with the drug Enalapril:
1 Before Enalapril After Enalapril Change Parameter (mmHg) (mmHg)
(mmHg) Mean Brachial Pressure Systolic 163 .+-. 15 155 .+-. 20 -8
Diastolic 85 .+-. 10 81 .+-. 10 -4 Pulse Pressure 78 .+-. 16 74
.+-. 20 -4 Mean 163 .+-. 15 155 .+-. 20 -8 Mean Central Pressure
Systolic 164 .+-. 18 156 .+-. 24 -8 Pulse Pressure 79 .+-. 19 75
.+-. 23 -4 Peripheral 2172 .+-. 508 2122 .+-. 462 -50 Resistance
Proximate Aortic 0.45 .+-. 0.24 0.49 .+-. 0.28 +0.04 Compliance
[0012] Mitchell GF et al, Omipatrilat Reduces Pulse Pressure and
Proximal Aortic Stiffness in Patients with Systolic Hypertension,
Circulation 2002:105:2955-2961. Although the results of this
therapy are favorable, the disadvantage is that such hypertensive
patients will be on such expensive medications for life, requiring
them to take one or more pills daily. Further, these medications
lack the desired efficacy in some patients while additionally
producing unwanted side-effects.
[0013] Accordingly, it is desired to formulate a different
treatment approach that achieves the same or better results as the
above-identified ACE inhibitor therapy, but avoids the associated
negative aspects of it. In this regard, one such alternate is
disclosed in U.S. Pat. No. 5,409,444 (Kensey) incorporated herein
by reference. While such a design may produce some improvement in
reducing high blood pressure, its efficacy remains limited by a
number of factors including an inability to transcutaneously change
compliance, poor energy conservation, an incapacity to measure and
transmit pressure, an inability to start compression until a
threshold pressure is reached, an inability to secure itself with
inflammation induced fibrosis, and many more. These drawbacks have
held the design back from widespread use in the medical community
for treatment of hypertension.
[0014] Thus, a need exists for an improved medical device and
method of use for absorbing aortic shock pressure, lacking the many
drawbacks of the previous design in addition to the price and side
effect constraints of medications.
OBJECTS AND SUMMARY OF THE INVENTION
[0015] One object of the present invention is to provide a method
and apparatus for absorbing aortic shock pressure.
[0016] Another object of the present invention is to provide a
method and device for changing the velocity, volume, and/or
pressure of blood flow from the left ventricle.
[0017] Yet another object of the present invention is to provide a
method and apparatus for reducing the work load of the heart in a
patient with congestive heart failure, hypertension, or being
normotensive.
[0018] Another object of the present invention is to provide a
method and device for increasing the compliance of a vascular
system.
[0019] Another object of the present invention is to provide a
method and device that overcomes the disadvantages of the prior
art.
[0020] Another object of the present invention is to provide a
device that has a pressure-volume relationship that is capacitive,
thus aiding in systolic dysfunction.
[0021] The device of the present invention also allows for the
treatment of diastolic heart failure/diastolic dysfunction. It has
recently been recognized that increased stiffness of the aortic and
great vessels may in part be responsible for dyspnea and dyspnea on
exertion. Thus, inserting a device that restores or enhances aortic
compliance will partially or completely relieve the dyspnea and
diastolic dysfunction as etiology.
[0022] The device of the present invention also allows for
treatment of orthostatic hypotension. A partial stenosis, less than
60-70%, will create little or no clinical effect at rest. As
increased flow occurs with orthostatic hypotension on arising, the
enhanced flow through a partial stenosis will result in a developed
gradient, supporting the central blood pressure. Moreover, a major
cause of orthostatic hypotension is medication. The ability to
partially or completely eliminate medication with the device will
also limit the orthostatic hypotension.
[0023] The present invention relates to passive medical devices
that absorb aortic pressure shock, restoring elasticity to a
cardiovascular system.
[0024] Specifically, the present invention modifies the compliance
of a vascular system by providing an elastic member, capable of
reducing peak pressure and blood flow from the heart. These
embodiments further allow for reduction of peak systolic pressure
while increasing diastolic pressure and flow. Additionally, these
embodiments can reduce the overall workload performed by the heart.
Thus, the present invention allows for improved cardiovascular
system functions, enhancing a patients health.
[0025] In one embodiment, the device consists of an anchoring
platform, having an elastic member with a passage for blood flow.
This device is implanted percutaneously into a desired vessel
location. The elastic member begins to give or create increased
volume, when blood pressure reaches a desired level. Additionally,
the spring constant of the elastic member may be externally
modified to change the compliance. By precisely modifying the
properties of the elastic member, normal arterial compliance may be
restored.
[0026] In this concept, the compliance is dynamic. Greater pressure
creates greater volume through an application of the Bernoulli
principle. The enhanced flow results in decreased intraluminal
pressure, pulling a portion of the device into the lumen as does
the sail on a sailboat. Some applications of the present invention
may require the phase angle to be inductive, in other words having
a phase angle that allows pressure to lead flow.
[0027] The different relationships of pressure and volumes will
result in different clinical features and behavior. The device also
can be made to function only above the determined set point.
[0028] The device is also dose independent. That is, the device
does not function to lower blood pressure at values less than the
set point at which it begins functioning. Giving a blood pressure
medication to a person with borderline low hypertension would act
to lower the pressure further than needed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a side view of one embodiment of the present
invention.
[0030] FIG. 2 is an end view of the embodiment shown in FIG. 1.
[0031] FIG. 3 is a side view of one embodiment of the present
invention in an aorta.
[0032] FIG. 4 is a side view of a parallel compliant embodiment of
the present invention.
[0033] FIG. 5 is side view of a single entry compliant embodiment
of the present invention.
[0034] FIG. 6 is a side view of an outer cuff-like embodiment of
the present invention.
[0035] FIG. 7 is a side view of a percutaneous compliant grabbing
embodiment of the present invention.
[0036] FIG. 8 is a side view of an internal/external compliant
embodiment of the present invention.
[0037] FIG. 9 is a side view of another embodiment of the
internal/external compliant device of the present invention.
[0038] FIG. 10 is an end view of a compliant vacuum chamber with
springs of the present invention.
[0039] FIG. 11 is a side view of another embodiment of a compliant
vacuum chamber with springs of the present invention.
[0040] FIG. 12 is a side view of multiple compliant devices used in
accordance with the present invention.
[0041] FIG. 13 is a side view of a filamentous compliant embodiment
of the present invention.
[0042] FIG. 14 is a sectional view of an embodiment of an elastic
member of the present invention.
[0043] FIG. 15 is a closer sectional view of the embodiment of an
elastic member of the present invention shown in FIG. 14.
[0044] FIG. 16 is a sectional view of another embodiment of an
elastic member of the present invention.
[0045] FIG. 17 is a sectional view of a compliant valve embodiment
of the present invention located between the aorta and IVC.
[0046] FIG. 18 is a sectional view of a compliant valve embodiment
of the present invention located within the heart chamber wall.
[0047] FIG. 19 is a sectional view of a compliant diaphragm
embodiment of the present invention located within the hear chamber
wall.
DETAILED DESCRIPTION OF THE INVENTION
[0048] Stent With Internal Absorber
[0049] Referring to FIGS. 1-3, a body lumen compliance device 100
in accordance with one preferred embodiment of the present
invention includes an anchoring structure 102 such as a stent, that
has an open passage 103 therethrough. Mounted on the anchoring
structure is an elastic member 101 that is positioned along at
least a portion of the length of the anchoring structure 102.
[0050] In the embodiment shown, the elastic member 101 is shorter
than the anchoring structure 102, thus leaving two exposed ends of
the structure 102. The exposed ends can be used for enhancing the
ability of the structure 102 to secure the entire device 100 at its
desired location.
[0051] In the embodiment shown, the elastic member 101 is disposed
internal to the anchoring structure 102. However, the elastic
member 101 could be disposed on an external surface of the
anchoring structure or could be made so as to be integrally woven
within the anchoring structure 102. Either approach is acceptable
so long as the elastic member provides the necessary elastic
function to the device as described in greater detail below.
[0052] Referring to FIG. 3, a preferred site for use of the body
lumen compliance device 100 in accordance with the present
invention is in the descending aorta 104 of a patient having
hypertension. In this regard, the body lumen compliance device 100
is situated such that the anchoring device 102 secures the device
100 against the internal walls of the descending aorta. The body
lumen compliance device 100 is secured in place so as to eliminate
migration but the elastic member 101 is positioned so as to provide
the full extent of its elastic properties.
[0053] As will be understood by one of ordinary skill in the art,
the pressure peaks encountered during the normal heart cycle by the
aorta can be summarized as follows:
[0054] Graph of Pressure Peaks
[0055] As such, in cases where the aorta has lost its compliance,
the pressure peaks exert undue stress on the heart and particularly
the left ventricle, requiring more energy, decreasing cardiac
efficiency, as discussed above.
[0056] This system may also find use in cases of heart failure,
where the heart pumps blood into the aorta in an inefficient
manner. This may be caused by elimination of the vascular
compliance through aortic stiffening. Such compliance elimination
corresponds to an impedance mismatch, yielding energy wastage in an
already failing heart. Restoration of the compliance, even in cases
of normal blood pressure, will render the heart more efficient, and
represent a therapy for heart failure.
[0057] In accordance with this embodiment of the invention, blood
that is pumped into the aorta by the left ventricle is directed
through the open passage 103 of the body lumen compliance device
100 and into the region of the device that includes the elastic
member 101. As pressure increases from the pumping of the left
ventricle beyond a desired pressure suitable for the patient, the
elastic member 101 then absorbs this greater pressure by expanding
its volume, so as to dilute the stress otherwise caused to the
heart. In this fashion the elastic member 101 operates in a manner
similar to a healthy aorta insofar as it "complies" or expands, and
damps the pressure spikes caused by normal heart pumping and thus
over time, greatly reduces the negative stress that is exerted on
the heart muscle.
[0058] Parallel Compliance Device
[0059] Referring to FIG. 4, in accordance with another preferred
embodiment of the present invention, a parallel body lumen
compliance device 200 includes parallel compliance structure 204,
having an open passage (not shown) therethrough. Each end of the
parallel body lumen compliance device 200 secures to a vessel 201,
allowing the open passage to fluidly connect to the interior of
vessel 201 through device entrance 202 and device exit 203.
Positioned along a portion of the length of the parallel body lumen
compliance device 200 is an elastic member 101.
[0060] Parallel compliance structure 204 may be composed of an
elastic membrane capable of providing the necessary structure to
the parallel body lumen compliance device 200 and further sealing
off the device from the body lumen as to prevent blood loss from
the vascular system. It should be understood by one of ordinary
skill in the art that a variety of materials, especially surgical
or prosthetic vascular materials, may be used for the parallel
compliance structure 204 providing they allow for blood containment
and to maintain the device structure.
[0061] In the embodiment shown, an elastic member 101 is secured to
a center region of the interior passage of parallel body lumen
compliance device 200. Alternatively, the elastic member 101 may
occupy a smaller region or stretch the entire length of parallel
compliance structure 204.
[0062] This preferred embodiment shows elastic member 101 as
secured within the passage, internal to the parallel body lumen
compliance device 200. Alternatively, elastic member 101 could be
disposed on the external surface of parallel compliance structure
204 or integrated together with compliance structure 204. Any of
these approaches are acceptable provided they allow for necessary
elastic function to the device as described further below.
[0063] In operation, blood is pumped into the vessel 201 and
directed into device entrance 202. Blood passes through the passage
of parallel body lumen compliance device 200 and back into the
vessel 201 through device exit 203. As a spike of blood pressure
pulses through the vessel 201, parallel body lumen compliance
device 200 redirects a portion of the blood volume passing by
device entrance 202 allowing elastic member 101 to absorb the
pressure increase so as to decrease the stress otherwise caused to
the heart. In this manner, the elastic member 101 mimics the
operation of a healthy vessel in that it complies and dampens
pressure spikes caused by a normal heart pumping.
[0064] Single Entry Compliance Device
[0065] Referring to FIG. 5, a single entry compliance device 300
includes a single entry compliance structure 301 having an internal
cavity and an elastic member 303 positioned along a portion of the
single entry compliance structure 301. Vessel opening 302 fluidly
connects the interior of single entry compliance device 300 with
the interior of vessel 201.
[0066] In this alternative preferred embodiment, single entry
compliance structure 301 may be composed of an elastic membrane
capable of providing the necessary structure to single entry
compliance device 300 and further sealing off the device from the
body lumen as to prevent blood loss from the vascular system. It
should be understood by one of ordinary skill in the art that a
variety of materials, especially surgical materials, may be used
for the single entry compliance structure 301 providing they allow
for blood containment and to maintain the device structure.
[0067] In this embodiment, the elastic member 303 is disposed onto
the inner surface of single entry compliance structure 301.
However, the elastic member 303 could be disposed on an external
surface of single entry compliance structure 301 or integrated into
the structure's surface. Either approach is acceptable so long as
the elastic member provides the necessary elastic function to the
device as described below.
[0068] Referring to FIG. 5, a preferred position for the use of the
single entry compliance device 300 is proximate a vessel 201, more
preferably in the descending aorta of a patient having a
hypertension condition. Such positioning allows vessel opening 302
to secure to vessel 201 while providing an open passage from the
interior of vessel 201 to the interior cavity of single entry
compliance device 300.
[0069] In operation, blood is pumped into the vessel and directed
through vessel opening 302 into the interior of the single entry
compliance device 300 that includes elastic member 301. As pressure
increases from the pumping of the heart beyond a desired pressure
suitable for the patient, the elastic member 301 then absorbs this
greater pressure so as to reduce the stress otherwise inflicted
upon the heart. The cardiovascular system of the patient is thus
able to function similar to that of a healthy patient, complying
with and reducing spikes in pressure cause by normal heart
pumping.
[0070] Outer Cuff-Like Compliance Device
[0071] Yet another preferred embodiment can be seen in FIG. 6. A
compliant outer cuff device 400 is shown having a structural band
401 and an elastic member 101 (not shown).
[0072] When in a closed state, compliant outer cuff device 400 has
an inner diameter being slightly smaller than the outer diameter of
a desired vessel location. Therefore, the compliant outer cuff
device 400 is secured around the outer diameter of a vessel 201,
slightly compressing the original vessel diameter. The compliant
outer cuff device 400 may have a number of mechanical devices for
fastening the cuff around the vessel 201, such as clasps, hooks, or
other securing devices, allowing for easy attachment to a desired
location.
[0073] The elastic member 101 may be disposed on the inside surface
of the structural band 401, as well as the outer surface, or even
interwoven into the structural band 401. Any of these approaches
will be acceptable so long as the elastic member 101 provides the
necessary elastic function to the device.
[0074] In the embodiment shown, blood is pumped through the vessel
201, further passing through the region slightly compressed by the
compliant outer cuff device 400. As pressure and volume increases
in the compressed region of vessel 201, compliant outer cuff device
400 expands, acting to absorb this greater pressure. In this
manner, the device acts to dilute and damp the natural pressure
spikes caused by the heart.
[0075] Percutaneous Grabbing Compliant Device
[0076] In yet another preferred embodiment shown in FIG. 7, a
grabbing compliant device 500 includes an anchor structure 503
having grabbing hooks 501 disposed about the outer surface of the
structure and a passageway throughout. Integrated with the anchor
structure 503 is an elastic member 502.
[0077] In the present embodiment, the elastic member 502 is
interwoven with the anchor structure 503. The elastic member 502
may also be disposed on the inner or outer surface of the anchor
structure 503. Either of these approaches may be acceptable
provided they allow for the necessary elastic function described
below.
[0078] The outer diameter of grabbing compliant device 500 may be
slightly smaller than the inner diameter of the vessel 201. Such
sizing allows the grabbing compliant device 500 to be
percutaneously placed into a vessel 201 at a desired location.
Grabbing hooks 501 covering the outer surface of the grabbing
compliant device 500 are secured to the inner wall of the vessel
201, allowing for inward compression of the vessel 201 around the
device.
[0079] In accordance with this embodiment of the invention, blood
is pumped into vessel 201 by the heart, being directed through the
compressed vessel region containing the grabbing compliant device
500. As blood pressure increases beyond a desired initial
threshold, the elastic member 502 expands, momentarily increasing
the diameter of the grabbing compliant device 500 and thus the
diameter of the vessel 201. In this manner, the elastic member 502
acts to absorb this pressure spike, mimicking the compliance of a
healthy vessel and greatly reducing the stress induced from normal
heart pumping.
[0080] Internal/External Compliance Chamber
[0081] FIGS. 8 and 9 refer to two similar preferred embodiments of
the present invention, illustrating internal/external compliant
devices being located both internal to and external to the aorta or
other vessel.
[0082] In FIG. 8, an internal/external balloon compliance device
600 includes an inner chamber 604 and outer chamber 603. The inner
chamber 604 is tubular in shape, but other geometries may be
employed so long as blocking of the blood flow in the aorta 602 is
avoided.
[0083] Inner chamber 604 and outer chamber 603 form a single,
continuous membrane having an inner cavity. Internal/external
balloon compliance device 600 is positioned through the aorta wall
602 at an aorta wall entry hole 601, which is sealed around the
device to prevent leakage of blood from the aorta while serving to
hold the device in place.
[0084] FIG. 9 illustrates a similar embodiment as a tubular
internal/external compliance device 700. Instead of a rounded,
spherical shape, the outer chamber 703 conforms to a tubular,
cylindrical shape. This cylindrical outer chamber 703 takes up less
room outside the aorta or other vessel, but otherwise may possesses
the same characteristics and benefits as the preferred embodiment
of FIG. 8. Further, these embodiments provide the advantage of
avoiding issues of working against absolute pressure instead of
relative pressure.
[0085] In an alternative preferred embodiment, the compliance
device is integral into a vascular graft, allowing for vascular
repair as well as the ability to limit hypertension.
[0086] According to the present preferred embodiment, the internal
cavity of the internal/external balloon compliance device 600 may
be about 20-25 ml of volume inside the aorta and about 50-500 ml of
volume outside the aorta. Varying volume amounts may be used, so
long as the volume of the inner chamber does not block a
significant portion of blood pumped through the aorta, the volume
of the outer chamber does not interfere with organs external to the
aorta, and the volume allows the device to provide a desired amount
of elasticity as described below.
[0087] In the embodiments of FIGS. 8 and 9, desired elasticity is
caused by adjusting the devices to pressure of about 40 mmHg, so as
to cause about 10-55 ml of fluid or gas to run in and out of the
aorta with each heartbeat. Additionally, the 10-55 ml of fluid flow
is allowed to pass to the outer chamber 603 within about 0.1
seconds. Such flow time may best accomplished by using a gas, but a
liquid may also be used. An additional port or valve opening may
also be added to the chamber to allow adjustment of the chamber
volume or pressure, as well as determine a threshold pressure to
begin working.
[0088] In accordance with this embodiment of the invention, the
outer membrane of the internal/external balloon compliance device
600 is composed of elastic biocompatible material, such as silicone
or urethane. Portions of the device may also be composed of
noncompliant material, so long as the overall desired compliance of
the device is achieved.
[0089] The device may be coated with a biocompatible configuration,
such as a microporus structure that encourages cell ingrowth, and
endothelialization, with a cellular tissue surface integral as a
result.
[0090] Referring to FIG. 8, blood is pumped into the aorta by the
left ventricle and is directed past the inner chamber 604 of the
internal/external balloon compliance device 600. As pressure
increases from the pumping of the left ventricle beyond a desired
pressure point, the inner chamber 604 compresses by pushing gas
into outer chamber 603, thus absorbing the momentarily increased
pressure that would otherwise cause stress to the cardiovascular
system. In this manner, internal/external balloon compliance device
600 provides characteristics similar to a healthy aorta and
represents a way of achieving the desired compliance in at least
the embodiments of FIGS. 1-9.
[0091] Pressure Sensitive Valve Device
[0092] FIG. 17 shows a further embodiment of the present invention.
A compliant valve device 1301 is composed of a pressure sensitive
valve 1305 secured within passageway 1304.
[0093] In one preferred embodiment, compliant valve device 1301 is
located between the aorta 1303 and the Inferior Vena Cava (IVC)
1302. Passageway 1304 secures to the aorta 1303 and IVC 1302,
creating a passage to the interior of each. Pressure sensitive
valve 1305 interrupts passageway 1304 preventing blood flow from
passing through.
[0094] As blood pressure increases in the aorta 1303, the pressure
sensitive valve 1305 opens at a predetermined level of blood
pressure, allowing a small volume of blood to pass through to the
IVC 1302. This redirection of a portion of blood reduces blood
volume, further reducing the pressure. As the pressure in the aorta
1303 falls, the pressure sensitive valve 1305 closes. Thus, for the
cost of a small volume of blood, about 20 ml, compliance is
returned to the vascular system.
[0095] A variety of different surgical valves are known to one
skilled in the art and may be used for pressure sensitive valve
1305, providing it allows for the above described properties.
[0096] FIG. 18 shows an alternate position of a compliant valve
device 1400 located in the heart chamber wall 1405 separating the
right heart chamber 1403 from the left heart chamber 1402.
Passageway 1401 is integrated into the heart chamber wall 1405,
forming a passage between the two chambers. Pressure sensitive
valve 1404 is secured within passageway 1401, preventing blood flow
from passing through. Or, in the alternate, the pressure sensitive
valve 1404 is simply inserted into the heart chamber wall.
[0097] When the blood pressure in the left ventricle increases
during a heart beat, the pressure sensitive valve opens a
predetermined level, allowing for a small volume of blood to pass
from the left heart chamber 1402 to the right heart chamber 1403.
As the pressure in the left heart chamber decreases, the valve
closes, preventing blood flow between chambers. Thus, for the price
of about 20 ml of blood redirection, compliance may be restored to
a vascular system.
[0098] In one preferred embodiment of the present invention, the
valve device 1305 and pressure sensitive valve 1404 can be based on
known valve technology, e.g., a duckbill valve concept, a pressure
relief valve concept, etc.
[0099] In another preferred embodiment, these valve devices can be
based on a venturi valve concept so as to limit the danger of
clotting. With the venturi valve, the valve is always open thus
decreasing the potential for the blood to come to rest on a
structure and thus causing a clot.
[0100] In yet another preferred embodiment, the valve devices could
be based on a feedback control loop. For example, the valve could
be actuated according to an electronic signal that is determined
based on diagnostic measurements of the patient's condition. For
example, an algorithm in a control module would evaluate such
parameters as a patient's blood pressure, heart rate, body
temperature, etc. and then arrive at a signal that opens or closes
the valve in a manner that best addresses those parameters.
[0101] FIG. 19 illustrates yet another preferred embodiment of the
present invention. A compliant diaphragm 1500 is composed of
anchoring device 1502 and distensible membrane 1501.
[0102] The compliant diaphragm 1500 is preferably located in heart
chamber wall 1405, between the left heart chamber 1402 and the
right heart chamber 1403. Anchoring device 1502 secures distensible
membrane 1501 within a sealed passage through the wall. Distensible
membrane 1501 is composed of a pliable, distensible, biocompatible
material, capable of stretching without breaking when pressure is
applied. A variety of materials are available and known to a person
of ordinary skill in the art to achieve the desired stretching
functionality.
[0103] Unlike the previous compliant valve embodiment, blood does
not pass between chambers of the heart. Instead, pressure increases
in the left heart chamber 1402 as the heart 1300 begins to beat. As
the pressure reaches a predetermined amount, the distensible
membrane 1501 is pushed into the right heart chamber 1403,
effectively increasing the volume of the left heart chamber. This
volume increase serves to reduce peak blood pressure, restoring
compliance and reducing stress and damage to the vascular
system.
[0104] In this fashion, the pressure pikes of the blood flow caused
by the beating of the heart are dampened by the above compliant
device embodiments, allowing a patient's vascular system to
approximate a more normal compliant function.
[0105] Both the compliant valve device 1301 and the compliant
diaphragm 1500 may be used in tandem with other embodiments of the
present invention, including the embodiments illustrated in FIGS.
1-9.
[0106] Vacuum Chamber With Spring Loading
[0107] FIG. 10 illustrates yet another preferred embodiment of the
present invention. This embodiment also describes the method of
achieving compliance and can be used as the elastic member with at
least the embodiments of FIGS. 1-9.
[0108] A vacuum chamber compliance device 700 is composed of rigid
wall 701 and elastic wall 702, sealed together to form an internal
cavity 703 and a central open passage 704 throughout.
[0109] In the present preferred embodiment, internal cavity 703 is
vacuum sealed, the gas having been initially partially or
completely removed. The internal cavity 703 is primarily held open
by support springs 705 which may be composed of a variety of
thermoplastic metals such as nitinol. Such thermoplastic metals
allow the support springs 705 to be variably compliant and
externally programmable by way of an external heat source, as
described in further detail below. By carefully adjusting the
support springs 705, a desired compliance may be obtained.
Alternatively, the chamber may be loaded with a predetermined
amount of gas, providing a further compliance variable.
[0110] The vacuum chamber compliance device 700 is anchored to the
interior of an aorta or other vessel by way of the outer non
compliant wall 701. The internal elastic wall 702 provides a
compliant, elastic membrane capable of stretching with increased
pressure against the support springs 705.
[0111] According to this preferred embodiment of the present
invention, blood is pumped into the aorta by the left ventricle and
is directed through the central open passage 704 of vacuum chamber
compliance device 700. As blood pressure increases beyond a desired
threshold, the springs compress to increase the internal diameter
of the device, absorbing the blood pressure spike. This absorption
of shock mimics the compliance of a healthy cardiovascular system,
decreasing overall stress.
[0112] Referring to FIG. 11, an alternate preferred embodiment of
the spring loaded vacuum chamber is also presented as a pillar
vacuum chamber compliance device 800, including an elastic membrane
805 sealed around support springs 801 extending away from the
device body. The inner cavity 803 of the device is sealed, forming
bellows 802 on the body side.
[0113] Internal cavity 803 is vacuum sealed, the gas having been
initially removed to form a partial or near-complete vacuum. The
internal cavity 803 is primarily held open by support springs 801
which may be composed of a variety of thermoplastic metals such as
nitinol. Such thermoplastic metals allow the support springs 801 to
be variably compliant and externally programmable by way of an
external heat source as described below. By carefully adjusting the
support springs 801, a desired compliance may be obtained.
[0114] Pillar vacuum chamber compliance device 800 is placed
percutaneously into an aorta or other vessel.
[0115] The pillar vacuum chamber compliance device 800 operates in
a similar fashion to the device of FIG. 10, in that blood is pumped
into the aorta by the left ventricle and is directed past the body
of the device. As blood pressure increases beyond a desired
threshold, the springs compress to decrease the body size of the
device, absorbing the blood pressure spike. This absorption of
shock mimics the compliance of a healthy cardiovascular system,
decreasing overall stress.
[0116] Multiple Compliance Devices
[0117] A further aspect of the present invention allows for the
utilization of multiple compliance devices strategically placed at
desired locations of the cardiovascular system. By utilizing
multiple compliance devices, the overall compliance of a patient's
cardiovascular system can be further adjusted to mimic that of a
young healthy system.
[0118] FIG. 12 illustrates such usage of the present invention in
an aorta 902 having a first compliant device 900 and a second
compliant device 901 positioned in a lower area of aorta 902. Any
of the previously mentioned embodiments of the present invention
may be used in such a multiple compliant system so long as they
function with the overall desired compliancy necessary to reduce
blood pressure spike induced stress.
[0119] Sandwiched Springs
[0120] As seen above, many of the aforementioned preferred
embodiments make use of an elastic member to provide underlying
elasticity and pliability, thus allowing the devices that use such
an elastic member to be compliant within a vascular system.
[0121] One such preferred embodiment of an elastic member can be
seen in FIGS. 14 and 15. Elastic member 101 includes an inner
elastic membrane 1100, forming an inner passage 1101. Outer elastic
membrane 1103 seals to the edges of inner elastic membrane 1100,
forming an inner cavity 1105 containing springs 1102.
[0122] In the embodiment shown, the inner elastic membrane 1100 and
outer elastic membrane 1103 are composed of an elastic,
biocompatible material allowing the device to expand and contract
as needed. Additionally, these elastic membranes contain bio-pores
1104 for cellular in-growth, allowing the device to become one with
the patient. Such in-growth is an important consideration to the
long-term health and survival of the compliance system in the
patient. Preferred pore size varies from about 20 to 200 microns
and the bio-pores 1104 may further connect through the aortic or
vessel wall in addition to interconnecting with each other to
maximize cellular in-growth. Optionally, the compliant vascular
device may posses inflammation inducing properties for fibrosis
stimulation which, in connection with the bio-pores 1104, serve to
further adhere the device to the vessel walls through in-growth of
fibrous tissue.
[0123] In the present preferred embodiment, springs 1102 are fixed
to the inner elastic membrane 1100 and outer elastic membrane 1103,
spanning the space inside inner cavity 1105. Inner cavity 1105 may
further contain a gas, liquid, or a vacuum to further modify the
compliance of device as discussed further below.
[0124] Springs 1102 are preferably composed of a thermo-plastic
metal such as nitinol. These materials allow the elastic member 101
to be variably compliant and externally programmable through the
use of a carefully directed heat source. The springs may be heated
transcutaneously with a number of different energy types, such as
radio frequency or ultra sonic energy. As the springs 1102 are
heated, their spring constants change, depending on the properties
of the material used.
[0125] In addition to changing the overall compliance of the
springs 1102, the pressure induced compliance threshold may be
modified. This value represents the minimum amount of pressure
required for the device to act in a compliant fashion. Increasing
the spring constant of the springs 1102 increases the threshold,
while decreasing the spring constant reduces the threshold. Thus,
the thermo-plastic metal of the springs 1102 allow a physician to
adjust the slope of compression, linearity/spring function shape,
cut points, and regulation threshold. The pressure within the
chamber may be externally modified by adding or subtracting
material from the chamber.
[0126] The maximum preferred volume of the compliant vascular
device is about 30 ml, or about the volume that might easily fit
into the descending thoracic aorta. The preferred compliance volume
is about 10-55 ml, meaning that the compliant vascular device will
change in volume by about that amount within a tenth of a second
from the natural aortic pressure change, typically about 90 mmHg to
130 mmHg. The spring should be carefully adjusted to stretch a
desired amount over a pressure range. Such adjustments may be made
in accordance with Hooke's law which states that a spring will
stretch over its elastic range roughly in proportion to the tension
or compression applied to it. Therefore, the geometry of the
chamber and spring may be such that about a 5% or 10% elongation of
the spring causes a 100% change in the volume of the chamber.
[0127] Unitary Elastic Member
[0128] Referring to FIG. 16, an unitary elastic member 1200 is
composed of a solid elastic material such as silicone, other
plastic polymers, rubbers, nitinol meshes, polyurethanes, and other
similar elastic materials.
[0129] An alternative preferred embodiment (not shown) of the
unitary elastic member 1200 includes springs completely embedded
within the elastic material. These springs may be pre-programmed
for a desired compliance before incorporation into the elastic
material.
[0130] Filamentous Network Elastic Member
[0131] FIG. 13 illustrates yet another preferred embodiment of the
present invention. A filamentous network elastic member 1000
includes a plurality of elastic filaments 1002, sealed within an
elastic membrane 1001.
[0132] The elastic filaments 1002 are composed of an elastic
material or springs enclosed in a pliable material, allowing the
structure to compress and reduce volume. By further arranging
multiple elastic filaments 1002 together in a radial configuration,
the filamentous network compliant device 1000 efficiently acts to
absorb pressure shock.
[0133] As the blood pressure increases, the elastic membrane 1001
pushes against the elastic filaments 1002. This pressure causes the
elastic filaments 1002 to not only compress closer to each other,
but themselves compress in size. Thus, as blood pressure increases
above a certain level, the filamentous network elastic member 1000
reduces in size, decreasing blood pressure and reducing the stress
associated with this increased pressure.
[0134] Such an embodiment of an elastic member may be used in
connection with any types of compliant devices, including those
described in this invention, so long as they allow for adequate
placement of the elastic member to absorb a desired amount of blood
pressure.
[0135] Biasing Substance
[0136] The above mentioned preferred embodiments of the compliant
vascular devices may have a media bias in the elastic member 101,
as seen in FIG. 1, or a media bias in the internal cavity, as seen
in FIG. 8. By modifying the media bias of a compliant device, the
overall compliance, and therefore the overall performance of the
device may be modified. Such media may include gas, such as
nitrogen or carbon dioxide, a liquid, such as water or blood, or
lack of material such as a partial or complete vacuum.
[0137] An inner cavity such as inner cavity 1105 in FIG. 15 or
chamber 603 in FIG. 8 may be accessed externally and filled or
emptied of media, modifying compliance of the device. A preferred
embodiment includes a connection to the subcutaneous tissues that
is accessible by needle procedure subcutaneously and into a conduit
that communicates with the compliance chamber. The injected
material may also have a chemical process that changes a chemical
composition within the chamber to alter compliance. These methods
of adjusting the media bias not only permit alteration of
compliance, but also maintaining proper compliance as the system
ages.
[0138] Pressure Spikes
[0139] The above mentioned preferred embodiments of the compliant
vascular devices may need to equalize air pressure/atmospheric
pressure to take best advantage of optimal dynamic range. An air or
gas based connection will bias the offset on the chamber's
elasticity to that of the ambient pressure in the body, reflecting
external pressure. A preferred embodiment for such venting includes
one or more venting spikes that connect from an inner chamber of
the compliance device to outside the aorta, such as the peritoneal
cavity or thorax. The connections may be in the form of spikes
containing a lumen, and may push through the aorta into the
surrounding cavity. The devices may be prong-like in configuration
and extend radially outward from the support device to safely
puncture the aortic wall.
[0140] Transducer
[0141] Any of the embodiments of the present invention may also
include a transducer 106 capable of telemetry outside the body, as
seen in FIG. 3. The transducer may measure such values as device
volume, flow outside the device, device pressure (inside), and the
pressure outside the device. Thus, this compliant vascular device
will permit measurement of the phase angle between any or all of
these parameters and permit appropriate adjustment of parameters to
effect a positive hemodynamic change. The pressure, volume, flow,
and velocity information may be used in a feed back loop to alter
the device pressure-volume relationship for optimal cardiovascular
system effects. Such effects may be lessening of ventricular work,
altering phase angles between pressure, velocity, flow, lowering
pressure or raising pressure. The device may also possess
programmable pressure-volume relationships from either external or
internal features. This may involve heating, cooling, or magnetic
means to alter the compliance.
[0142] The compliant vascular device may be implanted in a variety
of locations in the body such as the aorta or other vascular
vessels. Further, the device may be placed at renal arteries to
increase apparent pressure at the kidneys. There is an apparent
wave reflection point induced at the renal arteries to stimulate a
blood pressure reduction. The apparent pressure increase is induced
out-of-phase with volume/flow to limit the systemic effects of the
apparent pressure. This will induce compensatory renal feedback
mechanisms to lower systemic pressure through natural
mechanisms.
[0143] The device may also be placed in the carotid arteries to
alter local hemodynamics (pressure dynamics) at the crotid sinuses
providing specific biologic feedback.
[0144] AAA Repair With Specific Shock Absorber Compliance
[0145] The compliant vascular device described in the embodiments
above may also be used for aneurysm repair (thoracic, abdominal,
abdominal aortic, or elsewhere), particularly in connection with
abdominal aortic aneurysm repair (AAA) such as shown in U.S. Pat.
No. 6,344,052, which is herein incorporated by reference. The
standard AAA graft material is made expansile to absorb stroke
volume from the heart and create a re-phasing shift to compliance,
lowering systolic blood pressure. The device may or may not be
throughout the entire length of the system, including the iliac
limbs of the system. This generates greater lengths for volume
absorption. The device may stretch down into the iliac bifurcation
and beyond into the iliac portions of the graft to have a large
volume of absorption and limit the required distance of expansion.
Multifilar support may be included, with different filar supports
having differential expansion constants. The device may also have
great dynamic range, to prevent fatigue. The covering of the device
may be elastic/expansile as well to allow expansion. There is an
external, protective covering to serve as a safety layer that
prevents rupture by overexpansion as may occur in later stages of
the graft device.
[0146] Although the invention has been described in terms of
particular embodiments and applications, one of ordinary skill in
the art, in light of this teaching, can generate additional
embodiments and modifications without departing from the spirit of
or exceeding the scope of the claimed invention. Accordingly, it is
to be understood that the drawings and descriptions herein are
proffered by way of example to facilitate comprehension of the
invention and should not be construed to limit the scope
thereof.
* * * * *